The present disclosure relates to rotary electric machines, such as electric generators, alternators, and motors, rotatable in a single or opposite directions about an axis, and particularly to such rotary electric machines of the type that are liquid-cooled.
Rotary electric machines are increasingly being operated at higher internal temperatures, and there is an increasing need to provide improved cooling of such machines to enhance their performance and reliability. While air-cooling rotary electric machines is common, certain operating environments for such machines do not lend themselves well to air-cooling them. Such environments may, for example, provide little room about the machine for air circulation or exchange, position the machine in close proximity to heated components that adversely warm the cooling air directed to the machine, or ambient air may include contaminants (e.g., dust, chaff) that can clog cooling air passages of the machine, blocking airflow therethrough and preventing adequate cooling.
It is known to liquid cool rotary electric machines by including them in a cooling circuit dedicated to cooling the machine, or with other components to be liquid-cooled. Typically, such a circuit includes a pump for inducing coolant flow through the circuit and a heat exchanger for removing heat from the coolant, which may, for example, be water, oil, or a glycol solution. The coolant is provided under pressure into a coolant inlet of the machine, circulates therethrough and absorbs heat via convective heat transfer, and is expelled from the machine through a coolant outlet, the machine coolant inlet and outlet providing locations at which the machine is joined to the cooling circuit. Such cooling circuits are well-known and beyond the scope of the present disclosure, and are not further described in detail herein.
Minimizing the size of a rotary electric machine while maximizing the heat rejection from the machine is critical to its reliability and successful long term operation.